Subject: Gaussian/Counterpoise

From: David van der Spoel <[email-masked]>
Date: Thu, 17 Jan 2002 14:11:07 +0100 (CET)

Hi,

In g98 rel. a11 Gaussian have introduced a feature for computing the 
counterpoise correction to the energy. It is described in the release 
notes along with an example, a HF dimer. When I run the example (on Linux 
machine) I get strange oscillatory behaviour where the conformation 
fluctuates between the correct 
\
 \   ___    conformation and a linear one:  ___   ___

Furthermore, the SCF energy reported is sometimes the monomer energy and 
sometimes the dimer energy, although the Counterpoise corrected energy is 
decreasing monotonically. Without the Counterpoise correction the system 
converges as expected to the tilted conformation.

I see similar oscillatory behaviour in calculations of other systems. Is
this a Gaussian bug? 

Groeten, David.
________________________________________________________________________
Dr. David van der Spoel, 	Biomedical center, Dept. of Biochemistry
Husargatan 3, Box 576,  	75123 Uppsala, Sweden
phone:	46 18 471 4205		fax: 46 18 511 755
[email-masked]	[email-masked]   http://zorn.bmc.uu.se/~spoel
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